It is known that heart failure is a clinical syndrome characterised by distinctive symptoms resulting from cardiac output insufficient for needs of body organisms and is mostly induced by cardiac hypertrophy due to excessive load onto myocardium. That is, the cardiac hypertrophy induces change of myocardiac microstructure, failure of energy production mechanism with respect to myocardiac systole and increase of myocardiac oxygen consume, which induce in turn myocardiac hyposystole (cf. "Naikagakusho" (Internal Medical Text), Vol. 2, pages 66-69, issued by Yamanaka Shoten, Feb. 5, 1982). Besides, clinically, due to myocardiac hyposystole, cardiac output is decreased and thereby input into ventricle is disturbed, which induces venous congestion and pulmonary congestion, and then, symptoms such as dyspnea and systemic edema appear.
For the treatment of the heart failure with avoiding myocardiac hyposystole, there have hitherto been used digitalis medicaments having cardiotonic activity such as digitoxin, digoxine, etc., and xanthine medicaments such as caffeine, theophylline, etc. However, the digitalis medicaments have some problems in applicable diseases. That is, although the digitalis medicaments are well effective for low output heart failure, i.e. in the symptoms where the cardiac output is absolutely insufficient for body's needs, they are not so effective for high output heart failure, i.e. in the symptoms where the deficiency of cardiac output is comparatively low. Moreover, contrary to most other medicaments, the digitalis medicaments have less difference between the effective dose and the dose at which they show undesirable side effects, and when the medicaments are continuously administered, there are induced so-called digitalis toxicosis such as nausea, headache, bradycardia, extrasystole, anginal symptom, and the like. Besides, xanthine medicaments have advantageously both of cardiotonic and diuretic activities, but these activities are very weak, and hence, they are not so effective.